1. Field of the Invention
The invention relates to systems and methods for estimating sets of signal parameters used in respective waveform equations to model signal data and for choosing the equation that best models the signal data.
2. Discussion of the Related Art
In most wireless communications systems, parameters such as bandwidth and pulse shape are fixed during design. These parameters then drive the design of the radio hardware that transmits or receives the selected signal format.
However, in some applications these parameters are not known a priori. One example is cognitive radio, an emerging field where reconfigurable radio transceivers detect unused spectrum and intelligently utilize it without interfering with licensed users. Depending on local conditions, a cognitive radio might select any unused carrier frequency, and might also dynamically adapt signal bandwidth to fill available spectrum. Establishing initial contact requires a search of all signals that occupy a previously established frequency range, followed by a more detailed investigation of each.
Another example is reconnaissance and electronic warfare, especially the interception of signals from an unknown origin. In these applications, it is useful to quickly estimate basic signal parameters for a plurality of signals of unknown origin. In general, estimates of these parameters should be accurate enough to match the signal with a receiver's limited timing and frequency tracking loop capability.
While some previous signal parameter estimation techniques exist (see U.S. Pat. Nos. 6,690,746 and 7,158,588), they are generally limited to specific modulation types. The well-known symbol-rate spectral line estimator, for instance, functions only for digital modulations with specific pulse shapes. Other methods apply only to specific digital modulation formats (e.g. phase-shift keying but not quadrature-amplitude modulation).